Process for vulcanization of elastomers with a small amount of unsaturation



United States Patent 3,413,273 PROCESS FOR VULCANIZATION OF ELASTOMERS WITH A SMALL AMOUNT OF UNSATURATION Michel Jean Camille Alicot, Soisy-sous-Montmorency, and

Georges Raymond Henry Mingasson, Paris, France, assignors to Etablissements Kuhlmann, Paris, France No Drawing. Filed Aug. 2, 1966, Ser. No. 569,584 Claims priority, applicatioi; France, Aug. 12, 1965, 2 9

8,1 5 Claims. (Cl. 260-795) ABSTRACT OF THE DISCLOSURE Acceleration of the vulcanization of elastomers with a small amount of unsaturation is accomplished using a tin salt of the formula in which R and R are the same or different and represent alkyl, cycloalkyl or aryl groups which may be linked together by a bond so as to form a nitrogen-containing heterocyclic ring, n being equal to 2 or 4.

can be vulcanized with sulphur and vulcanization accelerators.

In the case of butyl rubber, for example, the elastomer is obtained by copolymerization of isobutylene with a small amount of a diolefine, generally isoprene. It is known that this elastomer, from the very fact of its small amount of unsaturation, is more difiicult to vulcanize than natural rubber, in the case of vulcanization with sulphur. It has also been attempted to increase the action of the standard accelerators by the addition of very active substances, the most used of which are certain metallic dialkyldithiocarbamates. Among these, tellurium diethyldithiocarbamate is most used, which indeed enables a good vulcanization of butyl rubber to be obtained. However, this product imparts a grey colour to the vulcanizate material which in some applications may be inconvenient.

In the case of the elastomers known as E.P.D.M., at least two monoolefines, for example ethylene and propylene, are copolymerized with at least one copolymerizable diene, for example dicyclopentadiene. Just like butyl rubber, these E.P.D.M. elastomers are more difficult to vulcanize with sulphur and the standard accelerators than natural rubber.

It has now been found that divalent or tetravalent tin dithiocarbamates enable a very good vulcanization of elastomers with a small amount of unsaturation to be obtained. In the case of butyl rubber, vulcanized materials of a very light colour can also be obtained while increased protection against deterioration clue to heat is ensured. In the case of the E.P.D.M. elastomers, these same tin dithiocarbamates likewise enable good residual deformation values to be obtained. v

The tin dithiocarbamates which may be used for carrying out the invention are represented by the general in which R and R are the same or different and represent ice alkyl, cycloalkyl or aryl groups which may be linked together by a bond so as to form a nitrogen-containing heterocyclic ring, 11 being equal to 2 or 4.

These derivatives may be prepared, for example, by double decomposition between a salt of tin of valency 2 or 4 and a salt of an N-substituted derivative of dithiocarbamic acid, as indicated below for the following products:

Divalent tin diethyldithiocarbamate (R=R1:C2H5, 71:2)

65 parts of anhydrous carbon disulphide are added to a solution of 128 parts of pure diethylamine in 1200 parts of anhydrous ethyl alcohol in a period of 1%. hours, at +10 C. with stirring, in an apparatus provided with a stirrer. After purging with a stream of dry nitrogen, a solution of 85 parts of anhydrous stannous chloride in 100 parts of anhydrous ethyl alcohol is added in a period of 30 minutes at the ambient temperature. After the introduction the mixture is stirred for a further 15 minutes and the solid filtered off, washed with alittle ethyl alcohol and dried under vacuum. 141 parts of a product are obtained with an instantaneous melting point of 107108 C. On recrystallization from ethyl alcohol, a product with an instantaneous melting point of 108109 C. is obtained which is in the form of light beige crystals.

Calculated: C, 28.93; -H, 4.82; N, 6.75; Sn, 28.62%. Found: C, 29.04; H, 5.18; N, 6.86; Sn, 27.93%.

The parts indicated are parts by weight as well as in the following account.

Tetravalent tin diethyldithiocarbamate (R=R1=C2H5, "=4) 30.5 parts of anhydrous carbon disulphide are added at +10 C. in a period of 1 /2 hours, with stirring, to a solution of 59.5 parts of pure diethylamine in 240 parts of anhydrous ethyl alcohol, in an apparatus provided with a stirrer. Stirring is continued for 15 minutes and then a solution of 26.6 parts of anhydrous stannic chloride in 40 parts of anhydrous ethyl alcohol is gradually added, still at +10" C. After the introduction is finished, the mixture is stirred for a further 30 minutes, and the solid filtered off, drained, washed with a little ethyl alcohol and dried under vacuum. 68 parts of tetravalent tin diethyl- EXAMPLE 1 The following mixtures are prepared, from which the products used according to the invention can be compared with tellurium diethyldithiocarbamate I II III IV Butyl rubber with 1.6% mol of unsaturation 100 100 100 Calcined kaol' 100 100 100 100 Stearic acid" 2 2 2 2 Zine oxide- 5 5 5 5 Paratfin oil 6 6 6 6 'Ietramethylthiuram disulphide. 1 l 1 1 2-mercaptobenzothiazole 0. 5 0. 5 0. 5 0. 5 Divalent tin dietliyldithiocarbamate. 1

Tetravalent tin diethyldithiocarbamate- Tellurium diethyldithiocarbamate 1 Sulphur 2 2 2 2 (a) Colour of the mixtures: Examination of the mix- 3 tures shows that those containing diand tetravalent tin diethyldithiocarbamates remain creamy white, the same colour as the control mixture I, although that containing the tellurium diethyldithiocarbamate has become grey.

(b) The table below gives the properties of the mix- 4 EXAMPLE 3 (a) The following mixtures are prepared, which show the properties of the vulcanized materials obtained on using the products of the invention:

.) tures defined above, the columns A to H having the fol- V VI VII VIII lowing significance: Terpolymer of ethylene and propylene,

Cknown its r3111 3500... 100 10g 100 100 arbonbac 'nown as air 1 F 140 14 140 140 A mlxture? Carbon black, knownasNoir SRF 6O 60 60 60 B-scorch time t according to Mooney Naphthenie 011 of \ziseosity according to C vu1anizatin 3545 according to Mooney 10 100 100 100 100 Dperiod of vulcanization in minutes at 245 C. Zinc oxidea. 5 5 5 E---modulus ofth e vulcanized material at 300% kg./cm. L5 L5 L 5 1' 5 F-resistance of the vulcanized material to rupture Q-IHBIOHDWDWO 5 Tetramethylthiuram disulp 1 e 1 1 1 1 Gstretch1ng of the vulcanized material in percent 15 Tetravalent 1111 diethyldithiocarbaniate 2 2 S ater-ial H bore hardness of the vulcamzgd m (b) Mooney tests: The scorch time t and the 1ndex vulcanization t -t were determined on the Mooney vis- A B C D E F G H cosimeter regulated at 120 C. and 140 C. using the large rotor. 10 6.8 58 1,045 35 2 r 20.0 12.7 3 t Mooney tests ati? g: 323 2g Mixtures 120C. 140C. 11 11.7 0.9 t1 tass t5 tat-t5 30 14.3 79 715 50 31 s; as 2 1%3 15 III 13.4 8.6 2.75 3.30 1.15

m2 81 23 2.35 3.25 1.05 W 13 5 9 1 1 312 3; r 8 46 (c) Dynamometric properties: A series of vulcanizag8 Z 38 1% trons was eifected at 160 C. for variable periods, on 2 30 mm. plates, then the dynamometr'ic properties of the vulcanizates thus obtained were determined:

Dynamometric properties of the Period of vulcanization at 160 C. in minutes vulcanizate Mixtures 30 Mmulus 100% vrL 1s 2s 31 a5 40 as 40 4o VIII- 20 35 45 47 45 50 49 51 43 5- 32122112 59 Mdulus at 200% VII. 32 47 57 09 7s 7s 79 s0 VIII. 49 55 s5 s9 92 97 04 94 vi' is? 25 Si 79 1 2 12 132 13 13g 99 0 Reslstame mpme'kgicmlv1r 51 7s 93 100 101 101 102 99 102 s 105 335 320 230 205 200 245 245 225 EXAMPLE 2 (d) Residual deformation tests: A test was effected of Th f u tut S re re may residual deformation after compression, at constant de- 6 0 Owing mm c we p p formation, on test samples vulcanized for 60 minutes at I n m 160 C. The test samples are crushed to 75% of their 50 initial thickness during 22 hours at 70 C. The residual ggfgi gg gfi g %111010unsiimmtion lg? igg $68 deformation is measured and expressed as a percentage Stearic acid--- 2 2 2 of the deformation applied according to the formula: iii ii' ii 2 E E 8Y3 0 f Tetramethyithluram disulphide 1 1 1 Residual deformation= 100 Tetrevalent tin diethyldithiocerbemate. 3 .3... 55 0 so Teumum dlethyldlthmarbamath" ij5""i '5 L5 in which E E; and E represent respectively the initial Sulphur The mixtures are vulcanized for 10 minutes at 155 C. and subjected to ageing in a Geer stove at C. for three weeks.

BEFORE AGEING Resistance to rupture,

Stretching at g. em. rupture, percent AFTER AGEING thickness, the final thickness and the thickness under com- 1. In the process for the vulcanization of elastomers having a small amount of unsaturation in which a vulcanization accelerator is incorporated into the mixture to be vulcanized, the improvement comprising using as the vulcanization accelerator a tin salt of the formula:

N-O-S Sn R. S n

75 in which R and R are the same or different and represent alkyl, cycloalkyl or aryl groups which may be linked References Cited together by a bond so as to form a nitrogen-containing UNITED STATES PATENTS heterocyclic ring, n being equal to 2 or 4.

2. Process according to claim 1 wherein the tin salt is 3,086,955 4/1963 Lemlszka 260 '79'5 divalent tin diethyldithiocarbamate. 5 2,696,492 12/1954 Butler 260-793 3. Process according to claim 1 wherein the tin salt OTHER REFERENCES is tetravalent tin diethyldithiocarba-mate.

4- Process according to claim 1 wherein the tin salt is Olliger et al.. vulcanization of Elastomers, 1964, p. 160. tetravalent tin dibutyldithiocarbamate. JOSEPH L SCHOFER, Primary Examiner herein the tin salt is 10 tetravalent tin diisobutyldithiocarbamate. DENENBERG Amstant Exammer' 

